Conventional modular plastic conveyor belts and chains are constructed of modular plastic links, or belt modules, arranged end to end and side to side in rows. Spaced-apart hinge elements extending from each end of the modules include aligned rod holes. The hinge elements along the leading end of a row of modules are interleaved with the hinge elements along the trailing end of an adjacent row. Hinge rods, journalled in the aligned rod holes of interleaved hinge elements, connect adjacent rows together end to end to form a conveyor belt of selected length and width capable of articulating about a drive sprocket or drum at the hinges formed between adjacent belt rows.
Belt motion and belt tension can cause the hinge rods to migrate along the hinge or to lengthen. If a rod is allowed to extend out of the hinge beyond the side of the belt, the rod can catch on conveyor structure or other objects and cause damage. Consequently, it is important that hinge rods be contained within the belt. Many conventional modular plastic conveyor belts use a sliding retention member that can be manually moved from a closed position occluding the rod holes to an open position in which the aligned rod holes are accessible for rod insertion or removal. To prevent the retention members from accidentally moving from the closed position to the open position while the belt is running, the retention member is designed to require a significant force to move it out of its closed position. Before a hinge rod can be inserted into the aligned rod holes, a retention member must be moved out of the way. Once the rod is fully inserted, the retention member may be returned to its original position. Sliding the retention member out of the way to allow access to the hinge, pushing the rod into the aligned rod holes, and sliding the retention member back into position occluding the rod holes and retaining the hinge rod is one of the most time-consuming and physically challenging steps in the assembly and repair of modular plastic conveyor belts. And, if the retention member is inadvertently left in its open position, the unconfined rod can work its way out the side of the belt while the belt is running.
Consequently, there is a need for a rod retention system for a modular plastic conveyor belt that is self-closing and does not require the time and physical effort of conventional systems.